1. Field of the Invention
The invention relates to a further improvement in the application of aqueous synthetic resin systems based on melamine resins and/or urea formaldehyde resins for rock consolidation or as cavity filling-agents.
2. Discussion of Related Art
The improvement of rock mass strength by injection of auxiliary chemicals, usually prepared in water, has been described many times in the literature: compare for example DE-AS 11 53 698 as well as the publication H. Barthel "Improvement of rock mass strength by chemical injections", Bergb.-Wiss. 17 (1970), Volume 8, 281 to 285.
The subject of the prior application P 39 07 989.9 of the applicant is an improvement of this technology. The subject of the teaching of this prior protective right is aqueous preparations of acid-curable melamine resins and/or urea formaldehyde condensates for application in rock consolidation and/or cavity filling, e.g. in tunnel construction and mining, the improvement lying in the provision of an addition of zeolite NaA and/or hydrosodalite to increase the serviceability of the acid-curable aqueous resin preparations, and especially to prolong their stability in storage. The aqueous resin preparations contain in particular about 0.1 to 20 weight % and preferably about 0.5 suspended zeolite NaA or of the hydrosodalite. The co-utilization of urea, preferably in amounts of about 10 to 40 weight %, relative to the active substance content of the aqueous resin solution, can be provided for. The active substance content of curable melamine resins and/or urea formaldehyde condensates is usefully in the range of about 50 to 80 weight %, preferably in the range of about 55 to 75 weight %, relative in each case to the aqueous solution.
In the process, also claimed in the prior application, for rock consolidation, e.g. in tunnel construction and mining, the aqueous preparations of the melamine resins and/or urea formaldehyde condensates are mixed with an acid curing agent and then injected into the rock to be consolidated. Preferably aqueous solutions of mineral acids and especially an aqueous solution of phosphorous acid are used as the acid curing agent. It can be useful first to mix the mineral acids into aqueous electrolyte salt solutions, and then to intimately mix the curing agent solution with the resin solutions described at the outset and to inject them into the place of their application.
The aim of the present invention is the further development of the technical teaching of the named prior application of the applicant. The invention intends in particular to remove ecological doubts which can arise when aqueous solutions of phosphorous acids are used as curing agents. As is known, the undesirable increase in eutrophication of waters is attributed to water-soluble salts of acids of phosphorus. The entry of corresponding phosphorus compounds into rock can be at least undesirable if there is a risk of the leaching out of such water-soluble phosphorus compounds from the rock and the entry of the leached-out salt into surface waters.
The aim of the invention in the narrower sense is thus the selection of an acid-reacting curing agent for the stabilized resin systems of the prior application, with regard to which waters, do not exist.